L.s.,

Analysis indeed correct but some species are yet missing and need to be
added to the list by David:

other recent introductions in Western Europe from the New World:

Geukensia demissa - recent introduction into W.Europe (probably via
ballast water) - in W.Europe locally a plague in brackish water.

Mercenaria mercenaria - recent introduction on purpose into W.Europe
(local attempts to breed this species, and escaped locally into the
wild. S.W.Netherlands, Brittany)

Crassostrea virginica - recent introduction on purpose into W.Europe
(local attempts to breed this species, and escaped locally into the
wild. S.W.Netherlands, Brittany). Is being replaced rapidly by the
Pacific oyster, which adapts much better to the W.European marine
environment.

Ensis directus (or Ensis americanus) - probably introduced via ballast
water and at the moment almost a plague in the (sandy) S.E. part of the
North Sea. Has become a staple food for molluscivore birds and fishes in
the North Sea.

Petricola pholadiformis - old introduction, first collection on Dutch
coast around 1923. Probably via shipping. Has been constantly common
ever since.

possibly the Zonitoides could be an introduction from the old world into
the new world, since Zonitoides is a quite common genus over here.

All species above have been collected by most shell collectors in The
Netherlands (myself included) since these are quite common (for
Mercenaria and C.virginica, you have to know specific locations).

Sincerely, Erick

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